Microchip electrophoresis employs a microchip having an electrophoretic flow path including a separation flow path formed inside a sheet-like member. A sample such as DNA, RNA or protein introduced into one end of a separation flow path is electrophoresed in a direction toward the other end of the separation flow path for separation by a voltage applied between both ends of the separation flow path, followed by detection.
In microchip electrophoresis, an apparatus has been developed that repeatedly uses a single microchip having a single electrophoretic flow path to thereby automatically perform filling of a buffer solution, injection of a sample, and detection of electrophoresed/separated sample components (see JP-A No. 10-246721).
In order to raise a throughput in analysis, electrophoretic apparatuses have also been proposed, each of which employs a microchip provided with multiple flow paths. An example of such apparatuses is one which employs a single microchip provided with twelve sample introduction flow paths and one separation flow path. In the example apparatus, after filling of a separation buffer solution into the flow paths, dispensation of samples are manually performed on all of the sample introduction flow paths, and thereafter electrophoresis is sequentially performed in the separation flow path to separate the samples into components thereof and to thereby obtain data (see Bunseki, No. 5, pp. 267 to 270 (2002)).
In another apparatus, a single cartridge is provided with twelve flow paths constituted of capillaries in which filling of a separation buffer solution, dispensation of samples, separation by electrophoresis and acquisition of data are performed automatically (Electrophoresis, 2003, 24, pp. 93 to 95).
In a micro-liquid chromatography, a microchip has been provided with a liquid flow path including a separation column, and a sample introduced into one end of the separation column is migrated in a direction toward the other end of the separation column to thereby separate the sample into components, followed by analyzing the components (see Anal. Chem., 70, p. 3790 (1998)).
For detection of a sample component separated in a main flow path, fluorescence detection is performed. In a fluorescence detector, a specific place of the main flow path is irradiated, or the main flow path is irradiated along a prescribed length thereof, with an excitation light to detect a fluorescence emitted due to excitation of the sample component. In that case, an excitation wavelength and a fluorescence wavelength to be detected are each limited to one kind.
The above apparatuses described in the journals “Bunseki” and “Electrophoresis” are useful in terms of throughput. However, both apparatuses in the examples are operated only under limitations that an operation is based on a batch processing and the same separation buffer solution is used on twelve samples, on all of which analysis has to be performed in the same condition. That is, it is impossible to employ a different separation buffer solution on each sample and to individually set conditions for electrophoresis on respective samples.
In a case where the number of samples is less than 12, one or more electrophoretic flow paths are wastefully not used, leading to cost increasing.
In the fluorescence detection, for example, there is a case where respective samples, prepared by making DNA subjected to fluorescence labeling with Cy3 (excitation wavelength of 550 nm/fluorescence wavelength of 570 nm) and with Cy5 (excitation wavelength of 650 nm/fluorescence wavelength of 668 nm), are intended to be simultaneously analyzed. However, since there has hitherto been only one kind of combination of the excitation wavelength and the fluorescence wavelength, simultaneous analysis of two or more fluorescence has not been possible. The same problem can be seen in liquid chromatography.